The Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) standards provide specifications for high performance air interfaces for cellular mobile communication systems. LTE specifications are based on Global System for Mobile Communications (GSM) specifications and provide the upgrade path for 3G networks to evolve into partially-compliant 4G networks. LTE Advanced is an enhancement of the LTE standard that provides a fully-compliant 4G upgrade path for LTE and 3G networks.
A goal of 3GPPP and LTE is the simplification of the architecture of cellular mobile communication systems. One step in simplifying this architecture is transitioning from existing 3GPP universal mobile telecommunications system (UMTS) combined circuit and packet switched networks to pure internet protocol (IP) packet switched systems. Because the adoption of LTE is an ongoing process and many mobile devices are not yet compatible with LTE packet switched technologies, operators of LTE networks will typically run such networks in conjunction with circuit-switched networks. This allows network operators to service users of circuit-switched compatible devices as well as users of LTE compatible devices.